Postpartum Depressive Symptoms Linked to High Omega-6 and Low Omega-3 Intakes

Depressive illness during and after pregnancy affects from 10% to 40% of women worldwide, according to the World Health Organization. The occurrence of this burdensome condition is higher in less developed countries where treatment may be limited and difficult living conditions complicate the situation. Having previously had depressive illness and low nutrient intakes increase the risk for developing this troublesome condition. Improving the nutrient intakes of pregnant and nursing women may be one of the more feasible approaches to reducing the occurrence of depressive symptoms. Dietary fat, particularly the type of fatty acids in foods, is an important component of good maternal and infant nutrition. Increasingly, foods and diets contain large amounts of vegetable oils that are rich in omega-6 fatty acids. While these fatty acids are essential, their greater abundance in the food supply has crowded out the less widely distributed omega-3 fatty acids. Moreover, optimum maternal and infant health requires the long-chain omega-3s found mainly in fish and shellfish (omega-3s). Women who do not eat seafood have few other ways of obtaining these omega-3s from foods. In the study described here, researchers in Brazil examined the food and fatty acid intakes of women in the first trimester of pregnancy and the presence of depressive symptoms in the mothers 30 days after delivery. They wondered if the fatty acid intakes of these mothers might be related to the occurrence of postpartum depressive symptoms. Because of the difficulty in estimating small intakes of nutrients consumed infrequently from food intake information, the investigators obtained estimates only for the most abundant omega-6 and omega-3 fatty acids. These are linoleic and alpha-linolenic acids, respectively. The investigators calculated the ratio of these dietary fatty acids then looked at the occurrence of depressive symptoms in the different categories of fatty acid consumption. The investigators observed that mothers with high dietary ratios of omega-6 to omega-3 fatty acids were more likely to develop postpartum depressive symptoms compared with women having lower ratios. Mothers with intake ratios greater than 9.1 were 2½ times more likely to develop postpartum depressive symptoms compared with mothers whose intake ratios were below 9.1. For comparison, this ratio in US diets is about 10. The investigators also noted that the prevalence of depressive symptoms 30 days after delivery in these women was approximately 26%, much higher than the 11% prevalence previously reported for a sample of Brazilian women. These observations describe an association between high intakes of omega-6 fatty acids combined with low intakes of omega-3s and the risk of developing postpartum depressive symptoms. They do not demonstrate cause, but given what we know about the importance of long-chain omega-3s in brain structure and function, the link is suggestive. It would be highly informative to learn whether increasing the fish (or fish oil) intakes of pregnant women in this community would affect the risk of postpartum depressive symptoms compared with similar women who did not eat fish.